The present invention broadly relates to a function testing means for a photoelectric type smoke detector.
The present invention relates to a function testing means for a photoelectric smoke detector comprising a light-emitting element for detecting smoke, a light-receiving element for detecting smoke located at a position where the light from the light-emitting element is not directly received, a light-receiving element for supervision or monitoring which receives the light output of the light-emitting element for detecting smoke, and a light-emitting element for testing which emits a light output, corresponding to the received light output of the monitoring light-receiving element, to the light-receiving element for detecting smoke.
A photoelectric type smoke detector (hereinafter called a detector) could fail to give an alarm because of dirt or residue on the light-emitting surface of the light-emitting element or on the light-receiving surface of the light-receiving element, or could generate a false alarm because of dirt or residue on the wall surface in the labyrinth for detecting smoke. Therefore, it is required by law to periodically test the operation or functioning of the detector.
As a testing means of this type, there has been proposed a testing means which consists of a first light source which constantly emits light, a first light-receiving element located at a position where the light ray from the first light source does not arrive or impinge directly, a second light-receiving element provided on the optical axis of the first light source as well as a second light source provided on the light-receiving axis of the first light-receiving element and emitting light by matching a control signal from a fire control panel with the output of the second light-receiving element. An operational or function test can be carried out by emitting light from the second light source directly onto the first light-receiving element.
With this testing means, however, the second light source emits light only when output is generated by the light-receiving element and a control signal is received from the control panel to carry out the test. Therefore, it does not constantly supervise or monitor functioning of the detector.
Moreover, the amount of light emitted from the second light-emitting element in the above described situation does not vary with the output of the second light-receiving element and is always constant. In addition, this known testing means simply checks whether the detector is operating or not, and it is not possible to know the momentary sensitivity of the detector.
If the detector does not have normal sensitivity, it could produce a fire alarm with no real fire (false alarm) or, conversely, fail to respond to a real fire (alarm failure). These are serious defects for such a detector.